The first surgeon general's report on e-cigarettes, published in December, describes them as "an emerging public health threat." A "tip sheet for parents" that accompanied the report recommends evasion in response to the question, "Aren't e-cigarettes safer than conventional cigarettes?"

Curious teenagers (and adults) will have to look for an answer elsewhere, such as a study reported last week in the Annals of Internal Medicine. It confirmed that e-cigarettes are much less dangerous than the traditional, combustible sort, a fact that may come as a surprise to Americans who get their health information from government officials.

The researchers, led by Lion Shahab, a health psychologist at a University College London, tested the saliva and urine of 181 volunteers representing five groups: current smokers, current smokers who also use e-cigarettes, current smokers who also use nicotine replacement therapy products such as gum or patches, former smokers who have switched to e-cigarettes and former smokers who have switched to NRT. Shahab et al. found all five groups were receiving similar amounts of nicotine, but the switchers showed "substantially reduced levels of measured carcinogens and toxins."

The differences between vapers and smokers were dramatic, ranging from 57 percent reductions in three volatile organic compounds (ethylene oxide, acrylonitrile, and vinyl chloride) to 97 percent reductions in acrylonitrile (another VOC) and in a tobacco-specific nitrosamine, a potent carcinogen. The levels for vapers were at least as low as those for NRT users and in some cases lower, which is striking because NRT is widely accepted as a safe alternative to cigarettes.

This study, which involved long-term e-cigarette users, reinforces the results of a 2016 study finding large reductions in toxins and carcinogens among smokers who switched to vaping during a two-week experiment. Shahab et al.'s findings also jibe with chemical analyses of e-cigarette liquids and the aerosol they produce, work that led Public Health England to endorse an estimate that vaping is something like 95 percent safer than smoking.

The huge difference in risk between vaping and smoking is hardly surprising, since the former involves inhaling an aerosol that typically consists of propylene glycol, glycerin, water, flavoring, and nicotine, while the latter involves inhaling tobacco smoke, which contains thousands of chemicals, hundreds of which are toxic or carcinogenic. Yet misconceptions about the hazards of vaping are widespread, thanks to public health officials and anti-tobacco activists who seem intent on obscuring the truth.

In a recent survey of American adults by Vanderbilt Law School professor W. Kip Viscusi, 48 percent of respondents erroneously said e-cigarettes are either just as hazardous as the conventional kind or even more hazardous. Thirty-eight percent said e-cigarettes are less hazardous, but only 14 percent correctly said they are much less hazardous.

It's no wonder the public is confused, when the surgeon general, the Food and Drug Administration, and the U.S. Centers for Disease Control and Prevention portray e-cigarettes as a menace to public health instead of an opportunity to reduce smoking-related disease. All three inaccurately describe e-cigarettes as "tobacco products," falsely implying that the risks posed by vaping are similar to the risks posed by smoking.

Writing in the Philadelphia Inquirer a few weeks after Surgeon General Vivek Murthy's report came out, a local physician took her cue from him, dodging a straightforward question about the relative hazards of vaping and smoking with an irrelevant litany of speculative warnings. Such efforts to scare people away from e-cigarettes are positively pernicious and potentially lethal to the extent that they deter smokers from making a switch that could save their lives.

For Donald Trump, who was elected on promises of disruption and deregulation, an obvious target is the FDA's onerous new e-cigarette rules, which threaten to ruin thousands of businesses and stifle life-saving innovation. But Trump's freshly minted secretary of health and human services, Tom Price, needn't wait for revision of those regulations to experiment with a new approach to e-cigarettes. How about telling the truth?